Carburetor throttle valve positioner

ABSTRACT

One embodiment of a downdraft type carburetor has an idle system discharge port that is straddled by the idle speed and closed throttle positions of the throttle valve so as to permit idle speed fuel and air flow in one position and no flow in the other position; another embodiment has a conventional idle system with a transfer port straddling the edge of the throttle valve in the idle speed position of the throttle valve so as to permit normal idle speed fuel and air flow in this position, while being closed off or having its area that is exposed to the vacuum signal reduced in the closed position of the throttle valve to reduce idle channel flow; the two positions being controlled by a servo operatively engaging the throttle valve; the servo operation being controlled by intake manifold vacuum during engine deceleration operation to close the throttle valve, or upon engine shut off interrupting the ignition circuit to close the throttle valve with a subsequent return of the throttle valve to its curb idle position for engine restarting.

Harrison et al.

[ 1 CARBURETOR THROTTLE VALVE POSITIONER [75] Inventors: Robert S.Harrison, Detroit; Max W. Lunsford, Southfield, both of Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

[22] Filed: June 23, 1972 [21] Appl. No.: 265,873

Related US. Application Data [63] Continuation-impart of Ser. No.120,953, March 4,

1971, Pat. No. 3,682,148.

['52] US. Cl. 123/9'7 B, 123/103, 123/110, 123/198 DB, 123/DIG. 11 [51]Int. Cl. F02d 11/08, F02d 9/00, F02m 7/00 [58] Field of Search..123/DIG. 11, 97 B, 198 D, 123/198 DB, 198 DC, 179 BG,179 G, 180 B,103,110

[56] References Cited UN lTED STATES PATENTS 3,082,148 8/1972 Harrisonc! :11 123/198 DB X 3,491,717 l/i)7i) liurnin 123/198 DB X 1 1 Jan. 29,1974 Primary ExaminerAl Lawrence Smith [5 7] ABSTRACT One embodiment ofa downdraft type carburetor has an idle system discharge port that isstraddled by the idle speed and closed throttle positions of thethrottle valve so as to permit idle speed fuel and air flow in oneposition and no flow in the other position; another embodiment has aconventional idle system with a transfer port straddling the edge of thethrottle valve in the idle speed position of the throttle valve so as topermit normal idle speed fuel and air flow in this position, while beingclosed off or having its area that is exposed to the vacuum signalreduced in the closed position of the throttle valve to reduce idlechannel flow; the two positions being controlled by a servo 0perativelyengaging the throttle valve; the servo operation being controlled byintake manifold vacuum during engine deceleration operation to close thethrottle valve, or upon engine shut off interrupting the ignitioncircuit to close the throttle valve with a subsequent return of thethrottle valve to its curb idle position for engine restarting.

8 Claims, 2 Drawing Figures VAC 00 M efcsfz la/f CARBURETOR THROTTLEVALVE POSITIONER This application is a continuation-in-part of US.-Ser.No. l20,953, filed Mar. 4, l97l now U.S.Pat.No. 3,682,148, Robert S.Harrison and Max W. Lunsford, Carburetor Throttle Valve Positioner, andhaving a common assignee.

This invention relates, in general, to means for positioning thethrottle valve of a carburetor to minimize the emission of undesirableelements into the atmosphere. More particularly, it relates to a vacuumand electrically controlled servo to control fuel and air flow through acarburetor after engine shutdown and during engine decelerationoperating conditions to prevent engine dieseling and minimize thepassage of unburned hydrocarbons into the atmosphere.

The problem of engine dieseling after the engine has been shut off isrecognized. So long as the engine crankshaft continues to rotate, avacuum signal will be present in the carburetor throttle bore below thethrottle valve. This pulls idle system fuel and air into the hotcombustion chamber such that combustion is maintained for a few secondsor longer after the engine is shut off. This naturally is undesirable.Also, during engine deceleration, the very high manifold vacuumdeveloped interferes with the scavenging of the exhaust gases from thecombustion chamber. This results in incomplete burning of the idlesystem fuel pulled into the engine at this time, and, therefore, a largeamount of unburned hydrocarbons may pass out into the atmosphere.

This invention provides a carburetor throttle valve construction thatupon engine shutdown permits closing of the throttle valve to reduce thefuel and air flow below the level needed to overcome the frictionalresistance of the engine to sustain running; or, alternatively, providesa curb idle position for normally maintaining the engine at idlingspeed. An electrical circuit including the engine ignition key includesa valve to normally block the flow of manifold vacuum to a valvepositioning servo so that the throttle valve normally remains in itscurb idle position when not depressed. Upon shutting off of theignition, the latter valve opens to permit vacuum from a vacuumreservoir to actuate the servo and permit the throttle valve to close tothereby reduce the flow of fuel and air to the engine cylinders. Also,at high engine manifold vacuums indicative of an engine deceleratingoperating condition, say, for example, above l9 inches Hg, the vacuumactuates a switch to break the ignition circuit and thereby again permitthe servo to close the throttle valve.

The invention provides suitable apparatus for moving the throttle valveto its various positions to prevent engine dieseling and the emission ofunburned hydrocarbons into the exhaust system during engine deceleratingoperating conditions.

It is one of the objects of the invention, therefore, to provide acarburetor with a throttle valve positioner that will prevent enginedieseling and minimize the passage of unburned hydrocarbons into theexhaust system or atmosphere during engine decelerating operatingconditions.

It is also an object of the invention to provide the throttle valve of acarburetor with a servo that is con-- trolled by manifold vacuum to attimes close the throttle valve to either completely shut off or reduceflow of fuel and air to the engine cylinders; the servo itself beingcontrolled by the engine ignition system to close the throttle valveupon engine shutdown, or to close the throttle valve when the manifoldvacuum reaches a level indicative of engine deceleration operation.

It is a still further object of the invention to provide a carburetorwith a servo positioned throttle valve, the servo being vacuumcontrolled, the vacuum in turn being controlled by an electrical circuitincluding the engine ignition key and a valve controlled in response tohigh engine intake manifold vacuum indicative of engine decelerationoperation.

. Other objects, features and advantages of the invention will becomemore apparent upon reference to the succeeding detailed descriptionthereof, and to the drawing illustrating preferred embodiments thereof;wherein,

FIG. 1 illustrates schematically a portion of a carburetor embodying theinvention; and,

FIG. 2 is a view of a portion of the FIG. 1 showing, illustratinganother embodiment.

FIG. 1 illustrates a portion 10 of a downdraft type carburetor, althoughit will be clear as the description proceeds that the invention isequally applicable to other types of carburetors such as updraft orsidedraft, for example. More particularly, the carburetor is providedwith a main body portion 12 having a cylindrical bore 14 providing theconventional air/fuel induction passage 16. The latter is open at itsupper end 18 to air at essentially atmospheric pressure passing throughthe conventional air cleaner, not shown. At its lower end 20, passage 16is adapted to be connected to a conventional intake manifold, from whichthe air and fuel mixture passes to the engine cylinders, not shown, in aknown manner.

The flow of air and fuel through induction passage 16 is controlled inthis instance by a conventional throttle valve 22. The latter isrotatably mounted on a shaft 14 fixed for rotation in the side walls ofbody 12, in a known manner. A main fuel system is not shown, since itcan be any of many known types. The fuel would be' inducted into passage16 above the throttle valve in a known manner as a function of therotation of the valve from its fully closed dotted line position 34 toits wide open nearly vertical position, by the change in vacuum signal.

The carburetor also contains an idle system for supplying the necessaryfuel and air to the engine cylinders during engine idling speedoperation. This air and fuel is provided through the bypass passage 26past an adjustable needle valve 28 and through an orificed dischargeport 30 in an insert 32 into induction passage It will be noted in thisinstance that the discharge end of the idle system is located so as tobe straddled by the throttle valve between its fully closed dotted lineposition 34 and its curb idle or engine idle speed setting 36 shown infull lines. It will be clear that in the fully closed position 34, thevacuum existing below the throttle valve is cut off from the idlepassage 26 and therefore no fuel or air will flow at this time aspassage 26 is at ambient or atmospheric pressure at both ends. It willalso be seen that when the throttle valve is positioned in its idlespeed position 36, the discharge orifice 30 is subjected to the vacuumsignal below the throttle valve so as to cause the desired amount offuel and air to pass through the idle system to maintain the engine atthe present idling speed. It will also be clear that to prevent enginedieseling and to prevent the passage of any unburned fuel into theexhaust system and atmosphere during engine decelerating operatingconditions, it is desirable to move the throttle valve to its fullyclosed position to completely shut off the flow of fuel and air to theengine cylinders at these times.

FIG. 2 shows an alternative arrangement in which the invention isadapted for use with a conventional idle system. In this case, the flowis reduced below a level sustaining engine operation, upon engineshutdown and deceleration, as opposed to completely shutting off flow asdescribed in connection with FIG. 1. More particularly, FIG. 2 shows aconventional idle system for supplying the necessary fuel and air to theengine cylinders around the throttle valve during engine idling and offidle speed operation. A bypass passage or channel 26' contains the usualtransfer port 27 and a discharge port 30 controlled by an adjustableneedle valve 28.

The transfer port 27 is located so that its lower edge is aligned withthe edge of the throttle valve plate in its closed dotted line position34'. Alternatively, if desired, the transfer port can be locatedvertically in other positions relative to the throttle plate edge whenthe latter is in the closed position. The full line position 36, on theother hand, indicates the idle speed position of the throttle valve.

It will be clear that in the closed position 34', the idle passage areaexposed to the vacuum existing below the throttle valve is reduced fromthat when the throttle valve is in position 36. Therefore, a lowerquantity of fuel and air will flow at this time as the area of thetransfer port 27 above the throttle valve edge subjects passage 26 to anambient or atmospheric pressure bleed. The quantity flowable past theneedle valve at this time, therefore, is selected to be insufficient toprovide the torque necessary to overcome the engine frictlon.

It will also be seen that when the throttle valve is positioned in itsidle speed full line position 36, the transfer port area subjected tothe vacuum signal below the throttle valve is increased so as toincrease the amount of fuel and air to pass through the idle system toan amount needed to maintain the engine at idling speed.

Returning now to both FIGS. 1 and 2, to move the throttle valves 22, 22to the two positions, to accomplish the above, a lever or link 38 isfixed on or formed integral with the throttle valve shaft 24, 24 forrotation with it, a tension spring 40 biasing lever 38 in a clockwisedirection at all times to bias the throttle valve to its closed position34.

The lever 38 is adapted to be moved to the right, as seen in FIGS. 1 and2, to rotate the throttle valve counterclockwise to its engine idlespeed position 36, 36' by a servo 42. The latter includes a shell typehousing 44 divided into an atmospheric pressure chamber 46 and a vacuumchamber 48 by an annular flexible diaphragm 50. A vacuum line 56 opensinto chamber 48. A stem type actuator 52 is secured to diaphragm 50 andis normally biased against the end of lever 38 by means of a 1 spring54.

The force of spring 54 is chosen to be greater than that of returnspring 40 so that in its extended position,

rod 52 will rotate the throttle valve to the curb idle speed positions36, 36' shown. Manifold vacuum applied to servo chamber 48 on the otherhand will retract the rod 52 sufficient to allow spring 40 to rotate thethrottle valve 22, 22 to its dotted line fully closed position 34, 34.

The vacuum to line 56 emanates from an intake manifold vacuum port 60shown opening into the carburetor body portion 12 below the throttlevalve. It could equally be tapped directly into the intake manifoldportion 20. The intake manifold vacuum is sensed in a line 62 through arestriction or orifice 64 to a vacuum reservoir or accumulator indicatedschematically at 66. The orifice 64 prevents momentary fluctuations inthe manifold vacuum from affecting the level of vacuum in the reservoir66. More importantly, it prevents asudden decay in the manifold vacuumfrom equally suddenly decaying the vacuum in the reservoir 66.

The passage of vacuum from reservoir 66 to servo line 56 is controlledby a spring opened, electrically closed, valve 68 of the on-off type.More specifically, the valve body is shown provided with intersectingpassages 67, 56 into which projects the cone-shaped end 70 of a shuttlevalve. A spring 71 normally unseats the valve to open passage 67 topassage 56 to allow vacuum to be applied to the servo to fully close thethrottle valve.

Valve 68 also forms part of the conventional engine ignition circuit.The latter includes a known type of ignition key operated switch 72bridging or breaking the circuit from a battery 74 to the coil 76 of asolenoid or similar suitable type device of which valve 68 is a part.That is, the valve in this case can be the armature of a solenoid sothat when the coil 76 is energized, valve 68 will be forced rightwardlyagainst the force of spring 71 to seat the valve and fully close off thepassage 56.

The electrical circuit to valve 68 also includes a manifold vacuumcontrolled switch 80 adapted to make or break the circuit from theignition switch 72 to valve 68 as a function of the level of manifoldvacuum below the throttle valve. More particularly, the switch 80includes a plunger 82 biased to the left to bridge the contacts 84 ofthe switch by a spring 86. The latter operates in a chamber 88 connectedby a bore 90 to a manifold vacuum line 92 branched off intake manifoldvacuum port 60.

The spring 86 is chosen of a force sufficient to normally maintain thecontacts 84 bridged so long as engine intake manifold vacuum is below alevel of say, for example, 19 inches Hg. Above this level, the vacuum isindicative of the engine operating under deceleration operatingconditions, at which point it is desirable to fully close the throttlevalve to reduce the flow of further fuel and air to the enginecylinders. Accordingly, it will be seen that above 19 inches l-lg.,switch 82 will be moved rightwardly by vacuum to unbridge the contacts84 and open the circuit from the ignition switch 72 to valve 68. Thispermits spring 71 to open the valve 68 and flow vacuum from reservoir 66to the servo chamber 48 to fully close the throttle valve.

The operation of the system is believed to be clear from the abovedescription and from a consideration of the drawing. However, in brief,prior to engine start up, servo chambers 46 and 48 are at atmosphericpressure, permitting servo spring 54 to move lever 38 to crack open thethrottle valve to its idle speed position 36, 36'. As soon as the engineis cranked and started, the turning of the ignition key closes theswitch 72 to shut valve 68 and thereby prevent flow of vacuum to line56. Accordingly, the throttle valve remains in the position shown, withnormal engine idling fuel and air supply being inducted into the passage16 through the orificed discharge 30, 30'. Plunger 80 at this timebridges the contacts 84 since the manifold vacuum is below 19 inches Hg.The starting of the engine permits a build-up in vacuum level in thereservoir 66, for future use.

Assume now that the engine has been accelerated and the vehicle thenmoved, by the throttle valve being opened wider than the idle position,to accelerate the vehicle. It will be seen that this is permitted by thecounterclockwise rotation of lever 38 away from engagement with the endof rod 52 of servo 42. If now the vehicle. operator releases his footfrom the accelerator pedal, spring 40 will attempt to rotate thethrottle valve to its closed position 34, 34'. Intake manifold vacuumlevel will immediately increase to or above 19 inches Hg, indicative ofengine decelerating operating conditions. This will move plunger 80 tobreak the ignition circuit to valve 68 and permit the spring 78 to openthe valve. This immediately applies the vacuum in reservoir 66 to servochamber 48, retracting rod 52 and allowing spring 40 to fully close thethrottle valve. This shuts off (FIG. 1) or reduces (FIG. 2) all flow offuel and air to the engine cylinders, and minimizes any passage ofunburned fuel into the atmosphere.

Assume now that the engine is shut off by turning the ignition key. Thisopens the ignition switch 72 and again opens the valve 68 to permit thevacuum in reservoir 66 to flow to servo chamber 48 and retract rod 52 topermit closing of the throttle valve. There is a slight difference,however, in this operation as compared to the deceleration operation. Assoon as the engine is shut down, the intake manifold vacuum inport 60decays almost immediately to an atmospheric pressure level. However,because of the orifice or flow restrictor 64, the vacuum in reservoir 66is only slowly bled to atmospheric pressure. This delay of severalseconds is sufficient to permit vacuum to be applied to the servochamber 48 of a level sufficient to retract rod 52 and permit fullclosing of the throttle valve to reduce fuel and air flow. The timedelay of bleeding of the vacuum in reservoir 66 is sufficient,therefore, to prevent dieseling of the engine upon engine shutdown.

It will be noted, that once the vacuum in reservoir 66 does decay toatmospheric pressure, then servo chamber 48 will be at the same pressurelevel as chamber 46, and spring 54 will move the throttle valve to itsengine idle or engine start position 36, 36 shown.

Therefore, it will be seen that the invention provides a throttle valvepositioner that either completely shuts off or reduces all flow of fueland air to the engine during high engine decelerating operatingconditions; prevents engine dieseling after the engine is shut off for aperiod of time sufficient to permit the engine to come to rest; and yetrepositions the throttle valve to an attitude providing engine starting.

While the invention has been showed in its preferred embodiments in thedrawing, it will be clear to those skilled in the arts to which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

We claim:

1. A carburetor throttle valve positioner comprising, in combination, anengine carburetor having an induction passage open to atmosphericpressure at one end and adapted to be connected to an engine intakemanifold at the opposite end so as to be subject to engine vacuumvarying in level from ambient atmospheric pressure at engine shutdown toa maximum subatmospheric pressure level during engine decelerationoperating conditions, a throttle valve rotatably mounted across saidpassage and movable from a first position essentially closing theinduction passage to an engine idle speed position and beyond to a wideopen throttle position, and return, for controlling flow through saidpassage, the carburetor including an idle fuel/air mixture passageconnected to the induction passage around the throttle valve and havingtransfer port means straddling at times the edge of the throttle valveand having a discharge end connected to the induction passage below thefirst closed throttle position so as to always provide an idle air/fuelmixture so long as the engine is running regardless of the position ofthe throttle valve whereby the idle passage is subjected to the engineto a manifold vacuum signal at one level when the throttle is at itsidle speed position and a lower level vacuum signal when the throttlevalve is in the first closed position and control means to move saidthrottle valve to said positions, said control means including firstmeans operatively biasing said throttle valve to an open throttleposition, and power means responsive to engine shutdown operation foreffecting initially a movement of said throttle valve to its firstclosed throtle position to reduce the flow of a fuel/air mixture throughsaid passage, and subsequently a movement of said throttle valve to anopen position for an engine starting operation.

2. A throttle positioner as in claim 1, including second means biasingsaid throttle valve to a closed position, said power means including avacuum servo having a spring extended, vacuum retracted, piston rod inits extended position operatively engaging and moving said throttlevalve to said engine starting position, and in its retracted positionpermitting said second means to close said throttle valve, said vacuummeans operatively acting on said rod to retract said rod in response toengine shutdown.

3. A throttle positioner as in claim 2, including means connecting saidvacuum means to said intake manifold.

4. A 'throttle positioner as in claim 1, said power means including avacuum servo, conduit means connecting said servo to said intakemanifold vacuum, onoff valve means in said conduit means spring biasedto an on position in response to engine shutdown to connect vacuum tosaid servo to close said throttle valve, and a vacuum reservoir in saidconduit means for maintaining a vacuum on said servo of a levelsufficient to close said throttle valve for a predetermined period afterdecay of the intake manifold vacuum until the decay in vacuum in saidreservoir permits said first means to bias said throttle valve to saidopen position.

5. A throttle positioner as in claim 4, including engine ignition meansincluding an ignition switch and an electrical circuit operablyconnecting said switch to said on-off valve for effecting movement ofthe same to an off position upon closing of said switch to effect enginestart-up to block the flow of said vacuum to said servo.

6. A throttle positioner as in claim 5, including manifold vacuumactuated circuit interrupting means operable in response to theattainment of a high vacuum level indicative of engine deceleratingoperation to break said circuit means and effect opening of said on-offvalve to close said throttle valve.

vcation of vacuum to said servo.

7 8 7. A throttle positioner as in claim 5, said on-off valve 8. Athrottle positioner as in claim 4, including flow Including spring meansblasmg 531d latter Valve to an restricting means in said conduit meansbetween said position permitting application of vacuum to said servo,said latter valve including electrical means energized in response toclosing of said ignition switch to move said latter valve to an offposition blocking appli-, Vacuum at engine shutdownmanifold vacuum andsaid reservoir for delaying decay of vacuum in said reservoir upon decayof manifold

1. A carburetor throttle valve positioner comprising, in combination, anengine carburetor having an induction passage open to atmosphericpressure at one end and adapted to be connected to an engine intakemanifold at the opposite end so as to be subject to engine vacuumvarying in level from ambient atmospheric pressure at engine shutdown toa maximum subatmospheric pressure level during engine decelerationoperating conditions, a throttle valve rotatably mounted across saidpassage and movable from a first position essentially closing theinduction passage to an engine idle speed position and beyond to a wideopen throttle position, and return, for controlling flow through saidpassage, the carburetor including an idle fuel/air mixture passageconnected to the induction passage around the throttle valve and havingtransfer port means straddling at times the edge of the throttle valveand having a discharge end connected to the induction passage below thefirst closed throttle position so as to always provide an idle air/fuelmixture so long as the engine is running regardless of the position ofthe throttle valve whereby the idle passage is subjected to the engineto a manifold vacuum signal at one level when the throttle is at itsidle speed position and a lower level vacuum signal when the throttlevalve is in the first closed position and control means to move saidthrottle valve to said positions, said control means including firstmeans operatively biasing said throttle valve to an open throttleposition, and power means responsive to engine shutdown operation foreffecting initially a movement of said throttle valve to its firstclosed throtle position to reduce the flow of a fuel/air mixture throughsaid passage, and subsequently a movement of said throttle valve to anopen position for an engine starting operation.
 2. A throttle positioneras in claim 1, including second means biasing said throttle valve to aclosed position, said power means including a vacuum servo having aspring extended, vacuum retracted, piston rod in its extended positionoperatively engaging and moving said throttle valve to said enginestarting position, and in its retracted position permitting said secondmeans to close said throttle valve, said vacuum means operatively actingon said rod to retract said rod in response to engine shutdown.
 3. Athrottle positioner as in claim 2, including means connecting saidvacuum means to said intake manifold.
 4. A throttle positioner as inclaim 1, said power means including a vacuum servo, conduit meansconnecting said servo to said intake manifold vacuum, on-off valve meansin said conduit means spring biased to an on position in response toengine shutdown to connect vacuum to said servo to close said throttlevalve, and a vacuum reservoir in said conduit means for maintaining avacuum on said servo of a level sufficient to close said throttle valvefor a predetermined period after decay of the intake manifold vacuumuntil the decay in vacuum in said reservoir permits said first means tobias said throttle valve to said open position.
 5. A throttle positioneras in claim 4, including engine ignition means including an ignitionswitch and an electrical circuit operably connecting said switch to saidon-off valve for effecting movement of the same to an off position uponclosing of said switch to effect engine start-up to block the flow ofsaid vacuum to said servo.
 6. A throttle positioner as in claim 5,including manifold vacuum actuated circuit interrupting means operablein response to the attainment of a high vacuum level indicative ofengine decelerating operation to break said circuit means and effectopening of said on-off valve to close said throttle valve.
 7. A throttlepositioner as in claim 5, said on-off valve including spring meansbiasing said latter valve to an on position permitting application ofvacuum to said servo, said latter valve including electrical meansenergized in response to closing of said ignition switch to move saidlatter valve to an off position blocking application of vacuum to saidservo.
 8. A throttle positioner as in claim 4, including flowrestricting means in said conduit means between said manifold vacuum andsaid reservoir for delaying decay of vacuum in said reservoir upon decayof manifold vacuum at engine shutdown.